An object ' $O$ ' is placed at a distance of 100 cm in front of a concave mirror of radius of curvat

Question

An object ' $O$ ' is placed at a distance of 100 cm in front of a concave mirror of radius of curvature 200 cm as shown in the figure. The object starts moving towards the mirror at a speed $2 \mathrm{~cm} / \mathrm{s}$. The position of the image from the mirror after 10 s will be at _______ cm .\

Professor PC Thomas Classes · Answer

(400): Distance of object, $u=100 \mathrm{~cm}$ Radius of curvature, $R=200 \mathrm{~cm}$\ Speed of object $=2 \mathrm{~cm} / \mathrm{s}$\ After 10 second, $s=v 	imes t=2 	imes 10=20 \mathrm{~cm}$\ Distance of object, $u^{\prime}=100-20=80 \mathrm{~cm}$\ $f=-100 \mathrm{~cm} \Rightarrow \frac{1}{v}+\frac{1}{u}=\frac{1}{f}$\ $\Rightarrow-\frac{1}{100}=\frac{1}{v}+\frac{1}{-80}$\ $\Rightarrow \quad v=400 \mathrm{~cm}$\